. . . "??115.2 Prohibition.(a) It shall be unlawful for a Federal contractor, as defined in ??115.1(a), to make, either directly or indirectly, any contribution or expenditure of money or other thing of value, or to promise expressly or impliedly to make any such contribution or expenditure to any political party, committee, or candidate for Federal office or to any person for any political purpose or us" .